linux-kernel - Re: [PATCH] sched: Avoid that __wait_on_bit

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Date:	Wed, 17 Aug 2016 19:30:27 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Bart Van Assche <bart.vanassche@...disk.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Neil Brown <neilb@...e.de>,
	Michael Shaver <jmshaver@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: Avoid that __wait_on_bit_lock() hangs

On 08/16, Bart Van Assche wrote:
>
> On 08/16/2016 06:06 AM, Oleg Nesterov wrote:
>> If only I could reproduce. Or at least understand what are you doing to
>> hit this bug ;)
>
> Hello Oleg,
>
> What I'm doing to hit this bug is to run the test script that is
> available at https://github.com/bvanassche/srp-test on a setup that is
> equipped with at least one InfiniBand adapter. I see the following
> possibilities for you to reproduce this:
> * Ask a colleague for access to an IB setup.
> * Add RoCE support to the srp-test script and run that script against a
>   v4.8 kernel + ib_srp-backport + SCST ib_srpt drivers. These last two
>   (out-of-tree) drivers namely support SRP over RoCE. The upstream
>   drivers not yet. The SRP-over-RoCE functionality will be sent
>   upstream as soon as standardization of this protocol by the T10
>   committee has finished (this work has already been started and will
>   probably be finished later this year).
>
> Please let me know if you need more information.

Heh ;) I can't understand any single word above.

So I'll give up. Previously you reported that this patch

	http://marc.info/?l=linux-kernel&m=147085570503588

the problem goes away. In this case the next one

	http://marc.info/?l=linux-kernel&m=147101858416463

could give us more info but you didn't try it so far (without other
changes).

It seems you find the root of this problem somewhere else, hopefully
you will resolve it soon.

Oleg.